Apparatus for making negatives



June 16, 1936.

F. T. POWERS 2,044,184

APPARATUS FOR MAKING NEGATIVES Filed May 1'7, 1954 5 Sheets-Sheet 1 June16, 1936.

F. T. POWERS APPARATUS FOR MAKING NEGATIVES Filed May 17, 1954 3Sheets-Sheefl 2 mv qa MC. Nm

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APPARATUS FOR MAKING NEGATIVES Filed May 17, 1934 3 SheeJS--Sl'ul 5 Fig5. X

INVENTOR Patented June 16, 1936 UNITED STATES PATENT- oFFlcE v2,044,184APPARATUS FOR MAKING NEGATIVES Frank T. Powers, Douglaston, N. Y.

Application May 17, 1934, Serial No. 726,086

10 Claims. (Cl. 95-81) My invention relates to the graphic arts and doneat one time, and-then insert a screen and more particularly to themaking of negatives for do the half tone work, or vice versa. This is ause in producing photomechanical printing plates. handicap where theWork is mixed, as it involves One object of my invention is to provide aholding up one class of work until the other class means and a methodfor making combination is completed. 5 negatives, by which term I meannegatives which When combination negatives, or negatives in are in parthalf tone negatives ,and inA part line which a portion of the picture ordesign being renegatives. Another object is to provide a means producedis to be in half tone and another portion and a method for making halftone drop out is to be line work, it has been the custom to make lnegatives, wherein the dots in the high light two negatives, one in halftone and one in line, l0

areas are dropped out in the operation of making and by mechanical meansto combine the two the negative. negatives to produce the desiredcombination.

Another object is to provide a means operable This is a slow, delicateand cumbersome process, from the exterior of a camera, for accuratelyand to obviate it such substitute devices as the l positioning a halftone screen plate in proper Ben Day process and others have been used.15 relation to the focal plane of the camera and to With the aid of mypresent invention, line remove the plate entirely out of the image fieldof negatives and half tone negatives may be made the camera at the willof the operator and Withalternately with practically no loss of time andout disturbing the adjustment of the camera with no manual handling ofthe screen plate,

or admitting light to the interior of the camera and consequently at norisk of damage to so 20 chamber. expensive and delicate a piece ofequipment.

Other objects and advantages of the invention Successive exposures madewith or Without a will be set forth in part hereinafter and in partscreen may, if desired, be upon the same or difwill be obvious herefrom,or may be learned by ferent sheets of light sensitive medium, thus espractice with the invention, the same being reenabling the operator toproduce on the same alized and attained by means of the instrumentallnegative both half tone and line work from the ities and combinationspointed out in the apsame copy, or from different copies. pended claims.My invention finds particularly advantageous Heretofore process camerashave been equipped applica-tion in connection with process cameras :owith adjustable devices for holding a half tone in which the lightsensitive medium is utilized screen plate within the image field inproper in the form of rolls, such as are exempliiied'in relation to thefocal plane of the image and for my Patents Nos. 1,832,656 and 1,909,424issued varying the distance between the screen plate November 17, 1931,and May 16th, 1933 respecand the focal plane. The proper distance be-`tively; but I do not confine the application of function of the numberof lines per inch on the. be 'applied to other forms of process cameraused screen and the ratio of reduction or enlargefor the making ofnegatives for line cuts and ment of the picture being made, a functionwhich half tones, or cameras in which it is desirable is well known toexpert photographers experito use a half tone screen for a part of thetime 40 enced in the making of half tone negatives. To and to operatewithout a screen for a part of the 40 place a half tone screen inposition in cameras time.. Y of this type, it has been necessary to openthe 0f the drawings:-

camera chamber and insert the screen plate in Fig. 1 is a section of acamera embodying the a, suitable holder provided therefor. 115theredevice taken on the lineAA of Fig. 2. after it is desired to make aline negative for Fig. 2 isthe front view oftheinterior. 45

the making of which no screen plate is used, it Fig. 3 is a front viewand has been necessary to open the camerachamber Fig. 4 is a section onthe line BB of the device. and remove the screen plate. This operationis Fig. 5 is a detail of the operating and intertime consuming, involvesthe hazard of accident locking mechanism. l fo to the very expensivescreen plate, and necessi- Fig. 6 is a design to be copied. 50 tates theprotection of the light sensitive medium Figs. 'I and 8 are frisketsused in copying the while the change is being made. It is, therefore,design. e. common to employ two cameras, one for-line In these drawings.which are intended to be work and one for half tone work, or else todivide illustrative' and explanatory 0f preferred ems; tween the screenplate and the focal plane is a my improvement to such cameras, since itmay 35A up or classify the work so that' all line cuts are bodiment ofthe present invention and not re- 55..

strictive thereof, I have shown my invention as applied to a processcamera of the type illustrated and described in my Patent No. 1,909,424,issued May 16, 1933, and to which reference may be made for descriptionof parts of the camera not shown and described herein.

The present invention is aimed toward a mechanism for inserting a halftone screen into, and removing it out of, the field of the image, foradjusting its distance from the focal plane of the image whilemaintaining the screen in accurate parallelism with the vfocal plane;and for accomplishing these movements from without the camera andwithout the necessity of opening the camera or of protecting the lightsensitive medium within the camera from light, While the movements andpositioning are taking place. It is further aimed at preventing improperor careless manipulation of the mechanism and to insure accuracy in thepositioning of the screen. Preferably I provide means for receiving andsupporting a half tone screen in a plane parallel to the focal plane andmeans for moving said supporting means toward or away from the focalplane, while maintaining said parallelism, and also means for movingsaid supporting means from a. position within the area of the field ofthe image to a position outside of said area and/or vice versa.` Meansare also provided for indicating on the exterior of the camera theposition of the screen, both as to its distance from the focal plane andwith respect to the image area. Means are further provided which preventa careless operator manipulating the said moving means in a manner or ina sequence which might result in injury to the mechanism or to thecostly half tone screen.

In the illustrative embodiment here shown, the numeral 6 designates theback of a copying camera within which is supported a box 1 which holdsthe supply of light sensitive medium in the form of rolls supported onshafts 8 and 9. The strips of light sensitive material are fed intoimage receiving positon by means of the feed rolls I0 and pressure rollsII. The box 1 is provided with a front plate I2, the side edges of whichrun in track ways I3, permitting limited vertical movement within thecamera back. The box 1 and its normal contents are counter-balanced bythe weight I4 attached to one end of chains I5, which engage sprocketsI6, I1 and I8, and attached at their other ends to lugs I1a on the frontof box 1. These sprockets are mounted respectively on shafts I9, 2li`and 2|, which are provided with bearings 22, 23 and 24, respectively,attached to the walls of the back. On one end of shaft I9 is mounted a'handle 25, which serves to rotate sprockets I6 to raise or lower box 1to the desired position.

Rotatably mounted on lower portion of the box 1, by means of the shaft26, arms 21 and links 28 and 29, is a presser plate 30,.by means ofwhich the membrane of light sensitive material 3l is pressed against aglass plate 3 2 held stationary andin a plane truly perpendicular to theoptical axis of the lens of the camera by the frame 33. The cameraisprovided with the usual bellows 34 and with lens and accessories notshown in the Y drawings.

With a camera of the foregoing description, or

with other forms of cameras, or other photographic or reproductionapparatus, my invention may be employed in variousembodiments, one ofwhich is herein described. y

Means for supporting a variety of sizes of half vertical movement.

tone screen plates, 35, consisting of a holder comprising an outerrectangular frame 36 and horizontal adjustable cross bars`31 and 38. Theupper cross bar 31 is provided with angle members 39 at each end, whichare adapted to slidingly flt into grooves 40 in the frame 36, permittinglimited The lower cross bar. 38 is provided at each end with anglemembers 4I having pins 42 and adapted to be moved laterally with respectto the cross bar 38 by means of knobs 43 attached thereto and to bepressed toward the ends of the bar 38 by springs 44 located in recessesin the bar.

In the lower portion of the side members of the frame 36 are recesses 45adapted to receive the ends of the cross bar 38. Within these recessesare holes 46 suitably spaced and ada'pted to receive the pins 42. By aninward pressure on the knobs 43, thus compressing the springs 44, theangle members 4I and the pins 42 may be disengaged from the recess 45and holes 46, permitting the bar 38 to be moved upward or downward toproperly position it to receive a half tone screen of the particularsize it is desired to use. The upper cross bar 31 is also slidable butis held in place on thel top edge of the screen by gravity and requiresno further anchoring. The angle plates 41 attached to cross bars 31 and38 clip the top and bottom edges of the screen and retain it inposition.

Means are provided for positioning the screen holding frame 36 withrespect to the focal plane spectively, of which the upper pair, 50 arepivoted on pins 52 rigidly attached to the camera back, and the lowerpair 5I are mounted on shaft 53 supported by bearings 54. The quadrants50 are pivotally connected to quadrants 5I by links 55. One end of shaft53 is provided with a lever 56 by means of which the quadrants may berotated through a limited arc to move the guides 48 carrying the screenframe 36 with respect to the focal plane of the camera. The frame 36engages and-is adapted to slide vertically in the guides 48. Thelocation of the quadrants 5I and 52 is near the four corners of theimage field of the camera and since they are of similar dimensions andconnected in pairs by link bars 55, any rotation of the shaft 53 movesthe guides 48 and the frame 36 equal amounts at each corner, thusmaintaining parallelism 'between any two positions of the frame 36 andthe guides 48, and also between the frame 36 and the focal plane of thecamera.

Means are provided for accurately positioning the screen frame to aknown distance from the focal plane of the camera, comprising the lev'er56, an indicator leaf 51 attached thereto, and a graduated scale 58attached to the side of camera back 6. This scale `is accuratelycalibrated to indicate the exact distance between the rear surface ofthe screen 35 and the surface of the light sensitive material 3|', whenit is pressed against the rear surface of the glass plate, 32, by thepresser plate, 30. Meansare provided for moving the half tone screen outof the image field of the camera, comprising a pair of link chains lowerends ofcurved bars,- 66. th'u'pper ends of which engage pins 66 attachedto frame 36. The crank handle, 61, provides i'or rotating shaft, 6|, andthereby raising or lowering the screen frame, 36, in the channel guides48 to position it either Within or without the image field.

When the half tone screen 35 iswithin the image eld and in operatingposition with respect to the focal plane, the screen and the screenrsupporting bars 31 and 38 are in a position such as is indicated by thedotted lines 31a and.` 38a in Fig. 1 and when in that position frame 36can not be moved upward to a position outside .the image neld withoutstriking frame 33. An attempt on the part of a careless oprator'to raisethe screen holder without first movingit forward by means of handle 56might result in breakage or injury of a very delicate and expensive halftone screen. Means are, therefore, provided to make it impossible toraise the screen except-when it is in the forward position indicated bythe full lines 'in Fig. 1. Said means comprise a notched disc 68 rigidlymounted on shaft 69 supported in bearings 18 and carrying a gear 1|meshing with pinion 12 on shaft 6I. Plvotally attached to the side ofthe camera back is a latch bar 13, having an loutwardly projecting lip14 adapted to drop into the notch 15 in disc 66. The lever 56, Whichcontrols the lateral position of the screen frame is provided with anextension 16 below the shaft 53 adapted to prevent the lifting of thelatch 13, except when the lever 56 is in its extreme position to theIScale 58.

In order to raise the screen frame 36 out-of the image eld of thecamera. the latch 13 must rst be lifted out of notch15.y This operationcan only be accomplished when the lever 56 is in the position in whichtheextension 16 does not interfere with the' lifting of the latch 13.-This position of the lever 56 is that corresponding to the forwardposition of the screen frame in which position it clears the frame 33. A

The ratio of the pinion 12- to the gear 1l is such that when thesprockets 60 are rotated a sufficient number of 'times to elevatevthescreen frame to the top of its travel, the disc 68 does not make acomplete revolution and therefore the notch 15 does not reach a positionin which the latch 13 can drop into it and so permit the movement oflever 56. Thus the rscreen frame 36 can only be moved from its forward.position toward the focal plane when it is in its lowest position, andthe'screen frame can only be raised when it is in its forward position.The handle 11 of the crank 61 is provided with a slidingpin 18, whichengages a hole 19 in a boss 80 attached to the side of the camera back.The sprockets 60 are of such diameter that a plurality of completerevolutions is required to carry the screen frame from one extremeposition to the other so that the pin 18 will be in position to engagethe hole 19 at both the upper and lower positions of the screen frame,thus securing it against accidental movement in either position.

In the practice of my invention I proceed as follows, when making acombination negative of a design such as is shown by way of example inFig. 6, having a portion, 8|, of the design thereon to be reproduced inhalf tone and a portion, 82, in line wor Irst prepare va. frisket 83 ofa transparent material, such as sheet celluloid or other suitablematerial. I place this sheet over the copy, and with a black ornonlight.

areas to be reproduced in half tone, as shown in' Fig. 8. I also providesuitable marks, pinholes4 or attachments for registeringthese sheets oftransparent material on the Acopy in the exact position vthat theyoccupied while the coating was being applied to them, as Ashown at X inFigs. 6, '7 and 8. I next place the copy-Fig. 6--in the copy holder of asuitable camera and place over it the sheet of transparent material,

Fig. 7, in the exact position which it occupied while being prepared, onwhich all areas to be reproduced by the half'tone method are coated. Ithen make an exposure on any suitable light sensitive medium, such asstrip film', or dry plate Aor wet plate, using suitable stop and time ofexposure to produce a satisfactory line negative, all of which is wellunderstood by those skilled in the art. I next replace the transparentsheet with-.the second sheet, Fig. 8, described above, being careful notto move the copy, and to register the sheet thereon in the exactposition which it`occupied while being prepared. I then place a halftone line screen in the image field of the camera between the lightsensitive medium and the lens and at the most suitable distance from thelight sensitive medium. 'I'his distance from the light sensitive mediumvaries with the number of lines per inch on the half tone screen andvwith the size of stop or diaphragm used in the lens, all of which iswell understood by those skilled in the art. I then make a secondexposure on the same light sensitive medium, thus producing two imagescombined thereon, one of those areas of the copy which is to bereproduced as line work, and a second of those areas which are to bereproduced in half tone work. The light sensitive medium may then beremoved from the camera and developed by usual methods.

I have found that if there are high-light areas in that portion of thecopy which is to be reprocompletely drop out" and do not appear on thefinished printing plate. 'I'his ,drop out exposure made without the halftone screen may be made on the copy being reproduced, or it may be madeon a whte or light surface, such as a sheet of paper or a surface havinga suitable degree of light reflecting quality. This method of droppingout the high lights by making a short exposure without the screen afterfirst having made a suitable exposure with the screen in place, may alsobe applied to the' making of straight half tones even when no line workis involved. In such cases no frisket is needed and the methodfollowedis to first make a normal exposure on the copy with a half tonescreen in the camera chamber at a suitable distance from the surface ofthe light sensitive medium. The screen is then removed from the imageeld of the camera and a short exposure made without the screen. Upondevelopment of the image on the light sensitive medium the small dots,which would normally be present in the high lights under the usualmethod, are obliterated or reduced to a degree that they drop out in thefinished plate.

Having described my invention in a manner that will enable one skilledin the art to practice it, I will now state what I believe to be new andnovel, and for which I pray that Letters Patient be granted.

I claim:

l. A process camera including in combination a light-tight casing,`means for presenting lightsensitive material in the focal plane of thecamera, means external to the c'asing for presenting a screen in theimage field and withdrawing it therefrom including a trackway, a screencarrier movable on the traclrway, and means for moving the trackway andcarrier toward and from the light-sensitive material to effect theproper separation for screens of different mesh.

2. A process camera including in combination a light-tight casing, meansforsupplying lightsensitive material located within the casing at oneside of the image field, means for presenting light-sensitive materialin the focal plane, a trackway' within the casing extending from oneside across the image ileld, a screen carrier movable along the trackwayinto and out of the image field, means operable from without the casingfor moving said screen carrier, into and out of the image ileld, andmeans operable from without the casing for moving the trackway andscreen carrier along the optical axis of the camera to successivelyparallel positions, which are perpendicular to said optical axis.

3. A process camera including in combination into said laterallyextending portion of the cas-v ing, a screen carrier mounted on thetrackway and provided with means for holding half-tone screens ofdifferent sizes, and means operable from without the casing for movingthe screen carrier along the trackway into the image field and into thelateral portion out of the image field and means for moving the trackwayand the'screen carrier mounted thereon, along the optical axis of thecamera, to positions perpendicular thereto.

4. A process camera including in combination means for presentinglight-sensitive material in the focal plane of the camera, means forpresenting a screen in the image field and withdrawing it therefromincluding a sectional trackway, a

screen carrier movable on the trackway, and means for moving a sectionof the trackway and carrier toward and from the light-sensitive materialto effect proper screen separation.

5. A process camera including in combination a light-tight casing, meansfor presenting lightsensitive material in the focal plane of the camera,means for moving a half-tone screen into and out of the image eld,including a trackway, a screen carrier running on the trackway, endlesssprocket chains connected to the carrier and sprocket wheels guiding andsupporting the chains and means external to the casing for rotating oneor more of the sprocket chains, and means for moving the trackway andthe screen carried thereby, toward and away from the lens of the camera.f

6. A process camera including in combination, a light-tight cameracasing, a half-tone screen within said casing, means for moving thescreen into and out of the image field, including a screen carrier and atrackway parallel to the focal plane, and means operable from withoutthe casing for simultaneously moving the trackway and screen carrieralong the optical axis of the camera, for varying the distance betweenthe screen and a light-sensitive element.

7. A process camera including in combination a light-tight casing, meansfor presenting lightsensitive material in the focal plane of the camera,means for guiding and moving a half-tone screen transversely into andout of the light path within the camera. the successive positions of thescreenbeing parallel and substantially perpendicular to the optical axisof the camera, and means, cooperating with said screen-moving,screen-guiding means, for moving the half-tone screen along the opticalaxis of the camera, when the said screen is in the light path Within thecamera, for focusing purposes.

8. A process camera including in combination a light-tight casing, meansfor presenting lightsensitive material in the focal plane of the camera,means for guiding and moving a half-tone screen transversely into andout of the light path within the camera, the successive positions of thescreen being parallel and substantially perpendicular to the opticalaxis of the camera, means, cooperating with said screen-moving andscreen-guiding means, for moving the half-tone screen along the opticalaxis of the camera, when the said screen is in the light path within thecamera, for focusing purposes, and means, cooperating with saidscreen-moving and screenfocusing means, for preventing the movement ofthe screen out of the light path, unless the screen has been placed in adefinite, predetermined position.

9. A process camera including in combination a. lens-carrying chamber, aguideway extending in said guideway, for carrying the screen into andout of the light path, means for operating said carrier from Without thecamera, and means cooperating with the guideway and the screen carrier,for moving the screen along the optical axis of the camera, for properplacement of the halftone screen with respect to the lens.

10. A process camera including in combination a lens chamber, a guidewayand housing therefor, extending laterally from the lens chamber, theguideway being substantially perpendicular to the axis of the camera, acarrier for a half-tone screen movable in said guideway for guiding thescreen into and out of the lens chamber, and means for moving theguideway and thereby the screen carrier, along the optical axis of thecamera.

FRANK T. POWERS.

